openrisc: fix trap for debugger breakpoint signalling

I have been working on getting native Linux GDB support working for the
OpenRISC port.  The trap signal handler here was wrong in a few ways.
During trap handling address (from the EEAR register) is not set by the
CPU, so it is not correct to use here.  We want to use trap as a
break-point so use TRAP_BRKPT.  Adding 4 to the pc was incorrect and
causing GDB to think the breakpoint was not hit.

Fixing these allows GDB to work now.
Signed-off-by: Stafford Horne <shorne@gmail.com>

arch/openrisc/kernel/traps.c

@@ -238,9 +238,7 @@ void __init trap_init(void)
 
 asmlinkage void do_trap(struct pt_regs *regs, unsigned long address)
 {
-	force_sig_fault(SIGTRAP, TRAP_TRACE, (void __user *)address);
-
-	regs->pc += 4;
+	force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)regs->pc);
 }
 
 asmlinkage void do_unaligned_access(struct pt_regs *regs, unsigned long address)